Fungal endophytes of the genus Neotyphodium (formerly Acremonium) infect a number of temperate climate Pooideae grasses. The Neotyphodium endophytes can produce alkaloids which are considered to confer degrees of pest and possibly disease protection upon the plants in which they naturally occur (Rowan and Latch, 1994; Blank and Gwinn, 1992). Resistance to drought conditions has also been claimed (Elberson and West, 1996). The Neotyphodium endophytes are vertically transmitted through the seed of the grasses and no natural horizontal transmission has been established (Leuchtmann, 1997).
Many of the predominating natural endophyte infections of improved grass cultivars used for pastoral agriculture production also cause significant animal disorders, for example fescue toxicoses (Stuedemann and Hoveland, 1988) and ryegrass-endophyte toxicosis (Fletcher et al., 1999). These may be complex toxic reactions by animals to alkaloids produced under a range of plant growth conditions. Significant economic loss within pastoral agriculture systems can occur due to such animal toxicoses. On the other hand presence of at least some endophytes may be essential for the competitive persistence of the chosen grass in a pasture (Elberson and West, 1996, Fletcher and Easton, 2000).
It has also been found that grass lines can be artificially infected with selected endophytes. Axenic cultures of endophytes can be used to infect grass seedlings, grown initially under sterile conditions (Latch and Christensen, 1985), which can then be selected for desirable qualities, and multiplied for commercial use. Three significant examples of this technology have been developed by AgResearch Ltd: GREENSTONE™ tetraploid hybrid ryegrass with ENDOSAFE™ endophyte (Tapper and Latch, 1999, NZ Patent 233083); various perennial and hybrid ryegrasses with ARI endophyte (Fletcher, 1999); and tall fescue cultivars with MaxQ™ (Bouton et al., 2002, U.S. Pat. No. 6,111,170).
Ryegrass-endophyte Toxicosis
Perennial ryegrass infected with its common wild-type endophyte, grown for both forage and turf, frequently produces compounds of the lolitrem sub-group of indole diterpenes in concentrations in herbage sufficient to cause the serious animal disorder known as ryegrass staggers. Lolitrem B is considered the most abundant active substance and concentrations in excess of about 2 ppm of herbage dry matter may result in clinical symptoms of ryegrass staggers in grazing sheep, cattle, deer and horses.
The same ryegrass-endophyte associations also produce ergovaline and perhaps other ergot alkaloids which are believed to cause other symptoms in grazing sheep, cattle, deer and horses commonly associated with the ryegrass-endophyte toxicosis syndrome. These symptoms may include hyperthermia in warm humid conditions as evidenced by increased rectal temperatures and respiration rates and depressed basal prolactin levels.
These responses are likely to be elicited at ergovaline concentrations in ryegrass pastures above 0.5 ppm. Ergovaline is also believed to be responsible for the depressed growth rates associated with the toxicosis syndrome. Increased faecal moisture and faecal soiling in sheep is also associated with ryegrass-endophyte toxicosis but causes have not been ascribed to any particular toxins.
The ryegrass staggers symptoms and overall effect of lolitrems may be enhanced by the presence in herbage of other toxins such as ergovaline.
Both lolitrem B and ergovaline concentrations tend to be higher in leaf sheath and seed heads of perennial ryegrass than in the roots or leaf blade. They also undergo seasonal variation with peaks in summer to autumn.
Enhanced Plant Protection with Reduced Toxicosis
Endophytes confer degrees of protection to host plants against biotic and abiotic stress. Some endophyte-derived alkaloids are known to be toxic or deterrent to insect pests. Peramine is a feeding deterrent for and lolitrem is toxic to Argentine stem weevil, (Listronotus bonariensis) (Rowan et al., 1990; Prestidge and Gallagher 1985). Ergovaline is deterrent to black beetle (Heteronychus arator) (Ball et al., 1997). Where these alkaloids are absent or in very low concentration in plants, infestation by such pests become a problem. Hence it can be seen from the above discussion that it is desirable to have a ryegrass that has low mammalian toxicity but which also contains deterrent and/or insecticidal compounds to help avoid insect or other pest problems.
It is an object of the present invention to provide an endophyte which produces alkaloid compounds in herbage of a host plant in a manner such that the usual combinations and concentrations of alkaloids in herbage as generally consumed by grazing animals in common farming practice does not cause practical toxicosis symptoms. It is a further object of the present invention to provide an endophyte which produces alkaloid compounds in herbage of a host plant that protects the grass from pasture and/or turf pests relative to equivalent endophyte-free grass.
It is a further object of the invention to provide an endophyte which does not produce detectable levels of toxins from the lolitrem group or ergovaline group.
It is a further object of the invention to provide an endophyte from the genus Neotyphodium that, in combination with a host grass, gives superior pest protection for forage and/or turf uses compared to either equivalent endophyte-free grass or grass infected with common wild-type Neotyphodium lolii. 
It is a further object of the invention to provide an endophyte which produces compounds from the class of janthitrem epoxides.
It is a still further object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications, cited in this specification are hereby incorporated by reference. No admission is made that any reference constititutes prior art. The discussion of the reference states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertiency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not consitute an admission that any of these documents forms parts of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.